Solid waste materials of the type typified by municipal waste have traditionally presented problems of disposal which have become increasingly critical in recent years as a result of not only a rapidly increasingly population but the compounding difficulty of a drastic increase in per capita production of solid waste. Conventionally, such solid waste has been disposed of by such means as incineration and landfill. Obviously, with the ever increasing concern with problems of natural resources and the dwindling supply of acreage suitable for landfill operations within a reasonable distance of population centers, both of these methods of solid waste disposal are becoming less acceptable.
At the same time that both population and the per capita production of refuse have been increasing, the consumption of paper products has also shown a dramatic rise. Largely accountable for this rise has been the supplanting of metal, wood and glass as packaging materials by paper and the increased use of paper disposables such as paper cups, plates, napkins, and in more recent years garments and bedding. As a result, the proportion of municipal refuse constituted by paper products presently approaches, and in all likelihood will soon exceed, half of the total amount of such refuse. Thus the composition of typical municipal refuse by undried weight has recently been analyzed by American Paper Institute as follows:
TABLE I ______________________________________ Glass, ceramics and stones 10% Metal 8% Wood 7% Garbage 12% Grass and dirt 10% Textiles 3% Plastic film 2% Leather, molded plastic and rubber 2% Paper 46% ______________________________________
In "An Interim Report; 1968 National Survey of Community Solid Waste Practices," U.S. Dept. of HEW, Environmental Control Administration, the typical composition of municipal refuse is given as follows:
TABLE II ______________________________________ Component Wet Basis % Dry Basis % ______________________________________ Metals 9 11 Glass 8 10 Dirt 3 3 Food Waste 19 17 Plastics 4 5 Yard Waste 4 4 Cloth 3 3 Wood 2 2 Paper 48 45 ______________________________________
In a similar analysis made by the assignee of the present invention, the constituents of municipal refuse for a particular community were found to be as follows:
TABLE III ______________________________________ Components Wet Basis % Dry Basis % ______________________________________ Metals, glass and dirt 20 27 Food wastes, cloth, plastic, wood, vegeta- tion and other organics 30 20 Paper 50 53 ______________________________________
Such wastes average 75 percent solids and 25 percent liquids, although the liquid portion has been observed to vary between 20 percent and 40 percent.